1. Field of the Invention
The present invention relates to an insulating paste, which contains glass having a low dielectric constant as the insulating component and from which a thick-film insulating layer is formed by printing, and also relates to a thick-film multi-layered printed circuit having insulating layers made of the paste.
2. Description of the Related Art
With the increase in the density of electronic devices and in the processing speed of them, it is desired to lower the dielectric constant of the insulating layers used in the thick-film multi-layered printed circuits thereof.
In general, the insulating layers of a thick-film multi-layered printed circuits are formed by applying a glass paste onto a substrate followed by firing. Conventionally, materials including crystalline glass or amorphous glass such as Al.sub.2 O.sub.3 --B.sub.2 O.sub.3 --SiO.sub.2 glass or the like, having a specific dielectric constant of 10 or so, along with a heat-resistant filler are used to form the insulating layers.
The conventional thick-film multi-layered printed circuits having insulating layers made of amorphous glass are obtained by firing an insulating layer of amorphous glass along with a thick-film conductor layer and a thick-film resistor layer which are on or under the insulating layer, at about 850.degree. C. Therefore, the interlayer diffusion of the components constituting the insulating layer of amorphous glass, the thick-film conductor layer and the thick-film resistor layer occurs during the firing and causes various problems in that the characteristics of the layers become degraded. Specifically, the insulating resistance of the insulating layer is lowered, the wiring resistance of the thick-film conductor layer is increased, and the resistance value and the resistance-temperature coefficient of the thick-film resistor layers are varied.